CO2 Lens & Mirror
ZnSe focusing lenses, GaAs output couplers, and molybdenum or silicon mirrors for CO2 cutters and engravers. Diameters and focal lengths matched to your machine, with 10.6 µm AR coating as standard.
CO2 optics are a different material problem
A CO2 laser emits at 10.6 µm, which is far enough into the infrared that ordinary optical glass is simply opaque. The materials that work are the ones that pass that wavelength: zinc selenide for lenses and output couplers, gallium arsenide for some windows and couplers, and metal or silicon for mirrors. Every handling rule that follows from that is different from the rules for fiber optics.
ZnSe is the workhorse. It transmits 10.6 µm well, takes a hard AR coating, and machines cleanly into the shapes a focusing lens needs. It is also soft, and its dust is hazardous. That single fact is behind most of the premature failures we see: not a bad lens, but a lens that was wiped with a dry tissue, or handled without gloves.
Where each optic sits in the beam path
- Output coupler. The partially reflective mirror at the laser resonator. It sets how much power leaves the tube, and it is a resonator part rather than a cutting-head part.
- Folding mirrors. Molybdenum or silicon mirrors that steer the beam from the resonator to the head. Molybdenum takes the abuse in high-power paths; silicon is used where weight and cost matter more.
- Focusing lens. The ZnSe lens in the head that converges the beam to the workpiece. This is the optic that gets changed most often, and the one most often damaged by contamination.
Matching the optic to the machine
| What to confirm | Why it matters | What we need |
|---|---|---|
| Material | ZnSe for lenses, GaAs or ZnSe for couplers, molybdenum or silicon for mirrors; they are not interchangeable | The position in the beam path, not just "a lens" |
| Diameter and thickness | Must seat correctly in the holder; a lens that sits proud will not hold focus | Measurement of the old optic, or a photo on a rule |
| Focal length | Sets spot size and depth of focus on the workpiece | Edge marking or the machine's parameter sheet |
| Coating | 10.6 µm AR as standard; a mismatched coating absorbs and heats | Machine type and power range |
| Power level | Determines whether a coated or uncoated optic, and which mirror material, is appropriate | Tube power and duty cycle |
Symptoms and what they usually mean
| Symptom | What it suggests | First check |
|---|---|---|
| Power drops steadily over weeks | Contamination or coating degradation on a lens or mirror | Inspect each optic in the path, starting at the one closest to the work |
| Cut has a wider kerf on one axis only | A folding mirror out of alignment rather than a bad lens | Check mirror mounts before replacing optics |
| Burn mark at the centre of the lens | Spatter reached the optic, or the assist gas was contaminated | Gas supply and nozzle condition as well as the lens |
| Haze or a milky film on a mirror | Condensation or oil mist from the air supply | Air dryer and filter condition |
| Engraving is uneven across the table | Beam alignment through the folding mirrors | Alignment, not optics replacement |
Handling rules for ZnSe, specifically
- Wear gloves. Do not touch the surface, and do not handle a lens with coolant or oil on your hands.
- Blow off loose dust before any contact cleaning, and never polish a ZnSe surface dry.
- Use lens tissue with an approved solvent, one pass, then discard the tissue; do not scrub.
- Treat a failed ZnSe optic as hazardous waste. Its dust is toxic, and a cracked lens should not go in the general bin.
- Store optics in their cases, face up, away from nozzles and tools.
Supply
We supply ZnSe focusing lenses, GaAs output couplers, and molybdenum or silicon mirrors for CO2 cutters and engravers, with diameters and focal lengths matched to your machine and 10.6 µm AR coating as standard. Send the machine model, the position in the beam path, and the diameter and focal length you need, and we will confirm material and coating before shipping. Wholesale and OEM supply available.